Electric switch



Nov. 6, 1951 A, F. Evi-:TT 2,573,895

ELECTRIC SWITCH Filed April 25 1951 24 lo [7a K FIGB l2 '9b u Isa 'lllllu' I 22 22 muh. l.

lo l? INVENTOR:

ARTHUR EVE TT Patented Nov. 6, 1951 UNITED STATES PATENT OFFICE ELECTRIC SWITCH Arthur F. Evett, Brookfield, Ill., assignor to Central Commercial Industries, Inc., Cook County, Ill., a corporation of Delaware Application April 25, 1951, Serial No. 222,821

(Cl. 20D-52) 3 Claims. 1

This invention relates to electric switches and more particularly to switches of the class primarily designed, adapted and intended for use in keying circuits wherein audio signal currents are selectively transmitted to an audio amplifying and translating system.

The invention is especially designed for use in tone signal generating and reproducing systems wherein tone signals at given tone frequencies are lselectively translated into audible sounds for musical-expression in response to actuation of the playing-keys of the keyboard of an electric organ or similar musical instrument.

An object of the invention is the provision oi an exceedingly simple, compact, light of weight. inexpensive switch assembly, the form and construction of the individual switches of which insure a good electrical connection between a signal supply source and the input circuit of the audio amplier of a sound translating device in response to actuation of the playingkeys of a conventional keyboard.

A further object is the provision of an assembly of electric switches, the general form and construction of which enables convenient application of the assembly to a musical instrument of conventional design, such as a piano or an electric organ.

Other objects and advantages of the invention will be apparent upon reference to the following description and the accompanying drawings, wherein:

Figure 1 is a perspective view of a portion of a conventional keyboard showing the invention applied thereto;

Figure 2 is a transverse section through the key switch assembly showing the grounded condition of one of the switches of said assembly, and

Figure 3 is a View similar to Figure 2 showing the switch in a making condition as is the case when an associated or coactive playing-key is depressed.

In carrying the invention into practice, use is made of a flat base member iii of suitable thickness and of non-conductive material, the same having a longitudinal strip Il, also oi non-conductive material disposed adjacent to one of the long edges of said base member. Said strip Il is provided with supporting means l2 of non-conductive material, the same serving to support two vertically spaced apart bus-bars or Contact elements I3 and it as shown. Contact element i3 is connected to ground as at I5, and element lll is connected to a current output lead Zfl, from which audio signal current impressed on said element may be conducted to an audio amplifying and translating system, not shown.

The base member I8 and all coactive parts of the switch contained thereby are formed and proportioned for accommodation of the unit in the space S between the bed plank P and playing-keys K of the keyboard of an electric organ, piano, or other keyboard musical instrument. The base member il will include as many key actuated leaf springs il as there are preassigned keys for controlling conduction of current to said amplifying and translating system. In Figure l, three such keys are illustrated. As each individual key will have an identical switch mechanism, it is thought that a detail description of one of said mechanisms will suiiice for all of them. It should be understood that the base member if! is of rectangular form and that the individual switches of the unit are arranged in longitudinal row formation with the individual switches longitudinally spaced apart from each other a distance sufficient to provide each of said keys with an assigned one of said switches.

Referring to Figures 2 and 3 it is noted that the leaf spring l l for the playing-key K has one of its ends riveted or otherwise suitably secured at ila to the base member Vl adjacent to the opposite longitudinal edge thereof, and that said spring is bent upwardly at i8 at an acute angle, thence vertically and upwardly, a short distance as at 59a, and finally upwardly at an acute angle to form a lip 20 which yieldingly bears against the under side of the key so that normally or in the absence oi playing pressure against the key, the latter is urged to an elevated position as shown at Figure 2. The width of each playing-key of a conventional piano or organ is approximately one-half inch. The spring il which is preferably formed of Phosphor bronze may be of any suitable gauge that will impose against the under side of the key a yielding force, tending to urge the key in an upward direction. Riveted or otherwise suitably secured to the base member ii! in any well known manner is a vertical, metallic bracket 2i, to which one end of a resilient contactor 2 is secured in a manner insuring a good electrical connection between the bracket and said contactor. Connected to the bracket is a current conductor fi'a from a signal supply source, not shown. This contactor comprises a single length of wire of suitable gauge, formed to provide a rectilinear coil spring. When mounted as shown at Figures 2 and 3, the contactor tends to assume a horizontal position, substantially parallel to the upper surface of said base member lil. The contacter passes through a relatively long horizontal opening ib in the strip i l, which opening is disposed relative to the contact elements le and ill so that said contactor passes through the space between said elements, thence through a metal eyeet in the vertical portion i90, of said` print il.

Under the normal tendency of the spring I'i, the key K is maintained in an elevated position and the free end ofthe contactor 2'3 is flexed upwardly and into good electrical engagement with contact element I3. The current flow is then to ground I5, via the contactor V22fand contact element I3.- When the playing-key is depressed as shown at Figure 3, the current now is to an output conductor 24, via contactor 22, which said conductor electrically connects to element I4. In the downward motion of the playing-key, the free end of the contactor is flexed `downwardly and brought into good electricaleng'agement with said contact element I4. The wound portions of the coil comprising the contactor are in abutting relation. The elements I3 and I4 each consists of a single length of conductive material of circular cross section and of suitable gauge. The external diameter of the contactor is proportioned relative to the distance that separates` element I3 from Yelement Ill so that in response to motion of the Vplaying-key, proper engagement of the contactor with said elements is assured and whereby, iiexure of the free end of the contactor insures a slight rubbing action between the contactor and said elements, thus maintaining the effective contact surfaces in a clean condition.

It is intended that any number of switches shall constitute a compact and relatively inexpensive unitary structure which can be placed in the space between the bed plank and the keyboard of an electric organ or similarly associated with the keyboard of a piano for use of the individual switch with the tone generating system disclosed in United States Letters Patent to Koehl, No. 2,250,065, issued July 22, 1941. However, this should not be taken to mean that the invention is limited to use in this environment.

In Figure 1 each playing-key is coactive with spring means S, the onice of which is to urge the key to a playing position. Tension of the spring means can be controlled by the conventional form of device shown at A.

I particularly stress the form4 and construction of a composite assembly of electric switches, placed side by side in a longitudinal row and designed for selective actuation of the playingkeys of a conventional keyboard. I stress also the form, simplicity and construction of the individual switches of said composite assembly and particularly the combination consisting of a leaf spring actuable by a playing-key and mechanically coactive with a contactor characterized by the tendency to assume a rectilinear form and to be flexed in response to stress upon said spring and thereby advanced into good electrical engagement with spaced apart electrical contact elements such as the herein disclosed longitudinal bus-bars I3 and |13 and with assurance that there is some wiping of the effective contact surfaces during operation of the switch.

In Figure 1 of the drawings, the space S is bounded by the under surfaces of the playingkeys K, the front face of the fulcrum bar X and the front face of the front block X of the bed plank P. The front to back dimensions of the l. An electric switch assembly comprising a y flat base member oi electrical insulating material l -of given length and width; a series of similar electric switches mounted onsaid member in longitudinal row formation with the individual switches spaced apart from each other, a pair of longitudinally disposed vertically spaced apart bus-bars supportedl by said member and electrically insulated from each other, each separate switch comprising a leaf spring having one end attached to said base member and its other end free and formed for coaction with a pivoted key to flex the spring inl response to pivotal motion of the key, and a resilient contactor having a free end projecting through the space between said bus-bars and connected with said leaf spring for exure of said contactor from a position of electrical engagement thereof with one of said bus-bars to a position of electrical engagement with the other bus-bar in response to said motion of the key.

2. An electric switch assembly comprising a at base member of electrical insulating material, a longitudinal row of similar electric switches mounted on said member with the individual switches spaced apart from each other, a pair of longitudinally disposed vertically spaced apart bus-bars sup-ported by said member and electrically insulated i`rcm each other, each separate switch comprising a contactor o laterally springy conductive material having a free end projecting through the space between said bus-bars and an end xed to said strip and formed for connection thereto of a current input conductor, and playing-key controlled means coactive with said contactor for exing same in respective directions first to electrically engage one and then the other of said bus-bars, said means including a vertically yieldable member attached at one of its ends to said strip and having its opposite end formed for free engagement with the under side of a playingkey to eiTect the aforementioned iiexure of said contactor in response to actuation of said key.

3. An electric switch organization comprising a base member of electrical insulating material, a pair of vertically spaced apart electrically conductive elements insulated from each other and supported by said base member', a contactor of laterally springy conductive material having a free end projecting through the space between said conductive elements and an end fixed to said base member and adapted to be connected to a current input conductor, and playing-key controlled means coactive with said contactor for iiexing same in respective directions rst to electrically engage one and then the other of said conductive elements, said means including a vertically yieldable member attached at one of its ends to said base member and having its opposite end formed for free engagement with the under side of a playing-key so as to erect the aforementioned exure of said contactor by and in response to actuation of said key.

ARTHUR F. EVETT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,487,977 Larsen Nov. 15, 1949 

